Initiators for polymerization

ABSTRACT

Initiators for cationic polymerization by thermal activation, photochemical activation (UV-irradiation) or activation by electron bombardment are compounds wherein a heterocyclic, aryl substituted or aryl ring is fused to a sulfonium moiety in combination with a non-nucleophilic anion. During the activation of the initiator, a carbon-sulfur bond is broken leading to formation of a sulfide and a carbonium ion within the same molecule. The carbonium ion initiates the polymerization.

The present invention relates to the use of compounds as initiators forcationic polymerization by means of thermal activation or photochemicalactivation (UV-irradiation) or activation by electron bombardment (EB).The polymerization-initiator consists of a heterocyclic, arylsubstitutedor with an arylring fused sulfonium salt in combination with anon-nucleophilic anion. During the activation of the initiator, acarbon-sulfur bond is broken leading to formation of a sulfide and acarbocation (carbenium ion) within the same molecule. The carbocationinitiates the polymerization. Since the activation does not lead tofragmentation of the initiator-molecule into smaller molecules, no lowmolecular weight sulfur-containing decomposition products form thatotherwise would evaporate or migrate from the polymer causing bad smell.The ring-opening cationic initiators in the present invention therebypossess great enviromental advantages both during the polymerization andin handling of the polymer products.

The present invention relates also to some compounds which are novelcompounds per se.

BACKGROUND

Cationic polymerization (for a recent review of the area, see:Comprehensive Polymer Science 1989, 3, 579 ff), in contrast to radicalpolymerization, is not inhibited by the presence of oxygen in air andproceeds after UV-initiation in the dark. Cationic polymerization isalso complementary to radical polymerization with respect topolymerizable monomers. Thus, electron rich carbon-carbon double bonds(e.g. alkenyl ethers) are easily cationically polymerized while acrylatemonomers are usually unreactive. Vinyl ethers however, do nothomopolymerize under radical polymerization conditions. Epoxides isanother commercially important class of monomers that polymerize readilyunder cationic conditions but are inert to radical polymerization.

The utility of cationic polymerization has strongly been tempered by thefact that previously developed cationic initiators have inferiortechnical properties such as unsatisfactory high initiation temperatureand poor solubility in monomer blends and smelly decomposition products.

Strong proton acids (e.g. HClO₄, HBF₄) or Lewis acids (e.g. AlCl₃, BF₃)initiate cationic polymerization of for example vinyl ethers andepoxides. These acids have a very limited utility in a technicalcontext, such as curing of a coating, mainly due to the immediatepolymerization that occurs upon mixing initiator and monomer, i.e. thesystem has no "pot life".

This problem has been circumvented by developing "latent proton acids".They are structurally recognized by being aryl-substituted"onium-salts", e.g. sulfonium-, iodonium-, or arsonium-salts, withnon-nucleophilic anions such as SbF₆ ⁻, AsF₆ ⁻, PF₆ ⁻, and BF₄ ⁻. Thesesalts are stable, latent sources of the corresponding strong Bronstedsacid HSbF₆, HAsF₆, and HBF₄ respectively, which are generated uponactivation and initiate the polymerization. The salts are inactive untilthe activation occurs. A majority of this class of latent initiatorsrequire photochemical activation (irradiation by UV-light). (Belg. Pat.828670, 1974; U.S. Pat. No. 3,981,897, 1976; Belg. Pat. 837782, 1970;Belg. Pat. 833472, 1976).

More recently, it has been shown that some sulfonium- and iodonium-saltscan be thermally activated and utilized for the initiation of a cationicpolymerization. Two methods for activation have been developed;redoxinitation (A. Ledwith, Polymer 1978, 19, 1217) and thermalinitiation (Jap. Pat. 63.221.111, 1988, [CA 1989, 111, 40092y],; Jap.Pat. 63223002 1988 [CA 1989, 110, 173955h]; S. P. Pappas and L. W. Hill,J. Coating Technol., 1981, 53,43; S. P. Pappas and H. B. Feng, "CationicPolymerization and Related Processes" ed. E. J. Goethals, AcademicPress, New York, 1984; T. Endo and H. Uno, J. Polym. Sci., Polym. Lett.Ed., 1985, 23, 359; T. Endo and H. Arita, Makromol. Chem., RapidCommun., 1985, 6, 137).

In common for these initiators is that the activation leads to afragmentation, dissociation of the initiator molecule into decompositionproducts of lower molecular weight (e.g. sulfide) along with theinitiation of a cationic polymerization, see figure.

    R.sub.3 S.sup.+ X.sup.- →R.sub.2 S+R.sup.+ X.sup.-

    R.sup.+ X.sup.- +M→RM.sup.+ X.sup.-

    RM.sup.+ X.sup.- +nM→RM.sub.n M.sup.+ X.sup.-

The deficiency of previously developed initiators (PDI) can thus besummarized in three points, where the present invention in all threeaspects furnishes considerable improvements:

1. PDI have poor solubility in monomers which generally have alipophilic character.

2. PDI yield low molecular decomposition products upon activation whoseemission may cause enviromental problems. This is especially pronouncedin the case of sulfonium salts where a low molecular sulfide is formed.

3. Commercially available initiators are limited to photochemicalactivation.

The activation of a thermal initiator involves a heterolytic cleavage ofa carbon-sulfur bond to form the most stabilized carbocation. Theactivation temperature for an alkyl-substituted sulfonium salt stronglydepends on the structure of the substituents. The activation temperaturedecreases if a more stabilized carbocation can be formed. Substituentsof resonance stabilizing ability (e.g. benzylic and allylic) lower thetemperature at which the cationic polymerization occurs.Electron-donating substituents (e.g. alkyl or alkoxy) in ortho or parapositions at the benzylic group further decrease the activationtemperature.

Besides controlling the initiation-temperature, the substituents have astrong influence on the solubility of the initiator-salt. Previouslydeveloped initiators have poor solubility in "solvent free" monomerssuch as epoxides, alkenyl ethers, or styrenes. This is due to the largepolarity difference between the initiator and the monomer blend.Hydrophobic substituents such as longer n-alkyls can moderate the polarcharacter of the initiator and improve its solubility properties inhydrophobic monomers.

Low molecular weight sulfides have a very strong and unpleasant smelleven at very low concentration levels (ppm-levels). They are formed atthe activation step and during the polymerization emission to theenvironment is very difficult to avoid. In addition, the remainingsulfide could at a later state migrate to the polymer surface and causea smelly polymer film. It is therefore very important to structurallymodify an initiator to avoid formation of low molecular weight sulfides.

The reaction scheme below illustrates the chemistry of a member of apreviously developed initiator where tetrahydrothiophene is formedduring the activation, followed by the initiation of a cationicpolymerization of a vinyl ether. ##STR1##

PRESENT INVENTION

The present invention relates to the use of compounds as initiators forcationic polymerization by means of thermal activation or photochemicalactivation (UV-irradiation) or activation by electron bombardment (EB).The polymerization-initiator consists of a heterocyclic, arylsubstitutedor with an arylring fused sulfonium salt in combination with anon-nucleophilic anion. During the activation of the initiator, acarbon-sulfur bond is broken leading to formation of a sulfide and acarbocation (carbenium ion) within the same molecule. The carbocationinitiates the polymerization. Since the activation does not lead tofragmentation of the initiator-molecule into smaller molecules, no lowmolecular weight sulfur-containing decomposition products from thatotherwise would evaporate or migrate from the polymer causing bad smell.The ring-opening cationic initiators in the present invention therebypossess great enviromental advantages both during the polymerization andin handling of the polymer products.

According to to another aspect of the invention novel compounds areprovided which are aryl substituted cyclic sulfonium salts of thestructural formula ##STR2## and which are selected fromS-methyl-2-phenyltetramethylenesulfonium hexafluoroantimonate,

S-methyl-2-phenyltetramethylenesulfonium hexafluorophosphate,

S-methyl-2-(p-tolyl)tetramethylenesulfonium hexafluoroantimonate,

S-methyl-2-(p-tolyl)tetramethylenesulfonium hexafluorophosphate,

S-methyl-2-(p-methoxyphenyl)tetramethylenesulfoniumhexafluoroantimonate,

S-methyl-2-(p-methoxyphenyl)tetramethylenesulfonium hexafluorophosphate,

S-ethyl-2-phenyltetramethylenesulfonium tetrafluoroborate,

S-ethyl-2-(p-tolyl)tetramethylenesulfonium tetrafluoroborate,

S-(n-butyl)-2-phenyltetramethylenesulfonium hexafluorophosphate or

S-(n-butyl)-2-(p-methoxyphenyl)tetramethylenesulfoniumhexafluorophosphate.

When using the compounds as initiators for cationic polymerization, thecompounds are activated by electron bombardment (EB), UV-irradiation, orthermally, causing a ring-opening reaction. The resulting carbocationand sulfide will be within the same molecule and consequently, no lowmolecular degradation fragments will be formed: ##STR3## Greatenvironmental advantages are achieved by using a ring-opening initiator,both during the polymerization and when handling the final product.

The reaction scheme below illustrates the activation of a ring-openingsulfonium salt with a non-nucleophilic anion according to thisinvention, followed by initiation and propagation of a cationicpolymerization of a vinyl ether. ##STR4##

In order to keep the sulfide formed after activation within the cationicfragment, it is according to the present invention of great importancethat:

i) The sulfonium salt is a heterocyclic, arylsubstituted or with anarylring fused, compound.

ii) The most stabilizing substituent at the sulfonium group is benzylicor substituted benzylic.

iii) The most stabilizing substituent is bonded to the sulfoniumcontaining heterocycle in order to promote the ring-opening formation ofthe carbocation.

To efficiently promote a cationic polymerization it also necessary thatthe anion (counter ion) is non-nucelophilic and that the sulfonium saltis soluble in the monomer mixture.

Suitable compounds, polymerizable via a cationic polymerization, thatcan be used with ring-opening initiators according to the presentinvention are epoxides, alkenyl ethers, cyclic ethers, lactones,oxetanes, styrenes, vinylarenes, alicyclic vinyl compounds (e.g.vinylcyclohexane), spiro otho esters, spiro ortho carbonates, bicyclicortho esters, isobutene, butadiene, isoprene, and phenol-formaldehyderesins.

The polymerization initiator according to the present invention is thusa heterocyclic, arylsubstituted or with an aryl-ring fused sulfoniumsalt in combination with a non-nucleophilic anion. Activation of thecyclic sulfonium salts according to present invention, is a ring-openingreaction forming a carbocation with a pendant sulfide group.Consequently, the sulfide will be covalently bonded to the initiatingcarbocationic fragment.

The polymerization initiator according to the present invention has oneof the following structural formulae ##STR5## wherein m=an integerbetween 3 and 5

n=an integer between 1 and 3

z=an integer between 0 and 3

y=an integer between 0 and 4

X=represents a group of the formula MY_(r) (1) or the formula Q(2),

wherein in where r is an integer between 4 and 6, examples of MY_(r) (1)is SbF₆, AsF₆, BF₄, and ClO₄, the formula Q(2) represents a sulfonicacid R-SO₃ wherein R is an alkyl or aryl group or a halogen-substituted,preferably F or Cl, alkyl or aryl group, examples of Q(2) is CF₃ SO₃ andCH₃ C₆ H₄ SO₃,

R¹ represents an alkyl or cycloalkyl group, preferably C₁ -C₂₀, or anaryl group,

R² represents hydrogen, an alkyl, alkenyl, cycloalkenyl or cycloalkylgroup, preferably C₁ -C₂₀, or aryl group, all R² being independent ofeach other,

R³ represents hydrogen, an alkyl, alkenyl, cycloalkenyl or cycloalkylgroup, preferably C₁ -C₂₀, or aryl group, all R³ being independent ofeach other,

R⁴ represents hydrogen, halogen, an alkenyl, for instance a vinyl group,a cycloalkenyl, an alkyl or cycloalkyl group, preferably C₁ -C₂₀, analkoxy or thioalkoxygroup, preferably C₁ -C₂₀, a hydroxyl- or alkyl(C₁-C₁₂)terminated poly(alkyleneoxide) group with up to 10 alkyleneoxideunits, an aryl group, an aryloxy or thioaryloxy group,

R⁵ represents halogen, an alkyl or cycloalkyl group, preferably C₁ -C₂₀,an alkoxy or thioalkoxy group, preferably C₁ -C₂₀, a hydroxyl- oralkyl(C₁ -C₁₂)terminated poly(alkyleneoxide) group with up to 10alkyleneoxide units, an aryl group, an aryloxy or thioaryloxy group,wherein in structure I R⁴ or R⁵ (y=1-2) also can be the group ##STR6##R⁶ represents hydrogen, an alkyl, alkenyl, cycloalkenyl or cycloalkylgroup, preferably C₁ -C₂₀, or an aryl group,

R⁷ represents hydrogen, an alkyl, alkenyl, cycloalkenyl or cycloalkylgroup, preferably C₁ -C₂₀, or an aryl group,

A represents ##STR7## or a single bond, R⁸ represents hydrogen, an alkylor cycloalkyl group, preferably C₁ -C₂₀, a hydroxyl- or alkyl(C₁-C₁₂)terminated poly(alkyleneoxide) group with up to 10 alkyleneoxideunits, an aryl group, an aryloxy or thioaryloxy group,

R⁹ represents hydrogen, an alkyl or cycloalkyl group, preferably C₁-C₂₀, a hydroxyl- or alkyl(C₁ -C₁₂)terminated poly(alkyleneoxide) groupwith up to 10 alkyleneoxide units, an aryl group, an aryloxy orthioaryloxy group, or

R⁸ and R⁹ together form an aryl ring fused with the heterocyclicsulfonium ring, said aryl ring optionally being substituted with a groupR¹⁰ which can be a halogen atom, a nitro group, an alkyl or cycloalkylgroup, preferably C₁ -C₂₀, alkoxy or tihoalkoxy group, preferably C₁-C₂₀, a hydroxyl- or alkyl(C₁ -C₁₂)terminated poly(alkyleneoxide) groupwith up to 10 alkyleneoxide units, an aryl group, an aryloxy orthioaryloxy group.

Some initiators in the present invention are novel compounds per sewhile others are previously known compounds. The latter however, havenot previously been described or suggested for use aspolymerization-initiators. The compounds which are novel per se all havethe general formula ##STR8## and areS-methyl-2-phenyltetramethylenesulfonium hexafluoroaantimonate,

S-methyl-2-phenyltetramethylenesulfonium hexafluorophosphate,

S-methyl-2-(p-tolyl)tetramethylenesulfonium hexafluoroantimonate,

S-methyl-2-(p-tolyl)tetramethylenesulfonium hexafluorophosphate,

S-methyl-2-(p-methoxyphenyl)tetramethylenesulfoniumhexafluoroantimonate,

S-methyl-2-(p-methoxyphenyl)tetramethylenesulfonium hexafluorophosphate,

S-ethyl-2-phenyltetramethylenesulfonium tetrafluoroborate,

S-ethyl-2-(p-tolyl)tetramethylenesulfonium tetrafluoroborate,

S-(n-butyl)-2-phenyltetramethylenesulfonium hexafluorophosphate or

S-(n-butyl)-2-(p-methoxyphenyl)tetramethylenesulfoniumhexafluorophosphate.

EXAMPLES

The invention is further illustrated by the following examples whichhowever are not intended to limit the scope of the invention in anyrespect.

Thermally induced cationic polymerisation

Two different difunctional cationically polymerizable monomerscontaining 1.0% by weight initiator were used. The initiator solutionswere prepared by dissolving the initiator in the monomer.

Monomer 1 consists of triethyleneglycol divinylether, TEGDVE (GAFChemical Corp.; DVE-3), with the following structure: ##STR9##

Monomer 2 consists of 3,4-epoxycyclohexylmethyl 3',4'-epoxycyclohexanecarboxylate, EEC (Union Carbide; UVR 6110), with the followingstructure: ##STR10##

The polymerizations were studied with a Perkin-Elmer DSC-7, differentialscanning calorimeter. The monomer/initiator solutions (3-5 mg) weresealed in aluminum pans before mounted into the calorimeter. Thetemperature scanning was 10° C./minute. The temperature range was20°-225° C., depending on the type of initiator used. TheDSC-thermograms generally showed a relatively sharp exothermic peak,resulting from the cationic polymerization initiated by the sulfoniumsalts. The results, peak temperature (Tp) and heat of polymerization(-ΔH) are displayed in table 1. The peak temperature (Tp) is defined asthe temperature at maximum heat flow and is approximatively the thetemperature at which the activation and initiation occur. The variationsin Tp (65°-157° C.) reflects the different ability of the substituentsto promote ring-opening and to stabilize the initiating carbocation. -ΔHis the heat of reaction per mole of monomer. The heat of reaction/moleis a measure of the monomer-conversion. However, in order to adequatelycalculate the monomer-conversion a theoretical heat of reaction isrequired for these monomers at different temperatures, that is notavailable. The cured films are however hard and non-smelling, which arerelevant technical criteria, so we conclude that 100% monomer-conversioncorresponds to 150-160 kJ/mol at 120°-140° C. for TEGDVE

Comparative example 1

In this example monomer 1 (TEGDVE) and benzyltetramethylenesulfoniumhexafluoroantimonate (BTMS⁺ SbF₆ ⁻) were used. This compound is a goodrepresentative for previously developed initiators (J. Polym. Sci.,Polym. Lett. Ed., 1985, 23, 359). The initiator is thermally cleavedaccording to the equation below: ##STR11## A hard crosslinked polymerwas found, but a strong odour of tetrahydrothiophene was noticable whenopening the aluminium pans. Tp and -ΔH are shown in table 1.

Comparative example 2

For this comparison, monomer 2(EEC) and BTMS⁺ SbF₆ ⁻, the same sulfoniumsalt initiator as in comparative example 1, were used. The thermallyinduced cleavage proceeds as described in comparative example 1. A hardcrosslinked polymer was found, but a strong odour oftetrahydropthiophene was noticable when opening the aluminium pans.

In the following examples different sulfonium salts of the structures Iand II according to the present invention were used as cationicinitiators. The sulfonium salts were all synthesized according to theprocedures presented in experimentals. In all polymerization studies,where different but analogous structures of I and II were examined, hardand crosslinked polymers were found. However, no detectable odour fromorganic sulfides or sulfur containing compounds were observed whenopening the aluminium pans. Tp and -ΔH are shown in table 1.

EXAMPLE 1

TEGDVE was used as monomer. S-Methyl-2-phenyltetramethylenesulfoniumhexafluoroantimonate according to structure A1 (below) was used asinitiator. Tp and -ΔH are shown in table 1.

EXAMPLE 2

EEC was used as monomer. S-Methyl-2-phenyltetramethylenesulfoniumhexafluoroantimonate according to structure A1 (below) was used asinitiator. Tp and -ΔH are shown in table 1.

EXAMPLE 3

TEGDVE was used as monomer. S-Methyl-2-phenyltetramethylenesulfoniumhexafluorophosphate according to structure A2 (below) was used asinitiator. Tp and -ΔH are shown in table 1.

EXAMPLE 4

EEC was used as monomer. S-Methyl-2-phenyltetramethylenesulfoniumhexafluorophosphate according to structure A2(below) was used asinitiator. Tp and -ΔH are shown in table 1.

EXAMPLE 5

TEGDVE was used as monomer. S-Methyl-2-(p-tolyl)tetramethylenesulfoniumhexafluoroantimonate according to structure A3 (below) was used asinitiator. Tp and -ΔH are shown in table 1.

EXAMPLE 6

EEC was used as monomer. S-Methyl-2-(p-tolyl)tetramethylenesulfoniumhexafluoroantimonate according to structure A3 (below) was used asinitiator. Tp and -ΔH are shown in table 1.

EXAMPLE 7

TEGDVE was used as monomer. S-Methyl-2-(p-tolyl)tetramethylenesulfoniumhexafluorophosphate according to structure A4 (below) was used asinitiator. Tp and -ΔH are shown in table 1.

EXAMPLE 8

TEGDVE was used as monomer.S-Methyl-2-(p-methoxyphenyl)tetramethylenesulfonium hexafluoroantimonateaccording to structure A5(below) was used as initiator. Tp and -ΔH areshown in table 1.

EXAMPLE 9

EEC was used as monomer.S-Methyl-2-(p-methoxyphenyl)tetramethylenesulfonium hexafluoroantimonateaccording to structure A5(below) was used as initiator. Tp and -ΔH areshown in table 1.

EXAMPLE 10

TEGDVE was used as monomer.S-Methyl-2-(p-methoxyphenyl)tetramethylenesulfonium hexafluorophosphateaccording to structure A6 (below) was used as initiator. Tp and -ΔH areshown in table 1.

EXAMPLE 11

EEC was used as monomer.S-Methyl-2-(p-methoxyphenyl)tetramethylenesulfonium hexafluorophosphateaccording to structure A6 (below) was used as initiator. Tp and -ΔH areshown in table 1.

EXAMPLE 12

TEGDVE was used as monomer. S-ethyl-2-phenyltetramethylenesulfoniumtetrafluoroborate according to structure A7 (below) was used asinitiator. Tp and -ΔH are shown in table 1.

EXAMPLE 13

TEGDVE was used as monomer. S-ethyl-2-(p-tolyl)tetramethylenesulfoniumtetrafluoroborate according to structure A8 (below) was used asinitiator. Tp and -ΔH are shown in table 1.

EXAMPLE 14

TEGDVE was used as monomer. S-(n-butyl)-2-phenyltetramethylenesulfoniumhexafluorophosphate according to structure A9 (below) was used asinitiator. Tp and -ΔH are shown in table 1.

EXAMPLE 15

TEGDVE was used as monomer.S-(n-butyl)-2-(p-methoxyphenyl)tetramethylenesulfoniumhexafluorophosphate according to structure A10 (below) was used asinitiator. Tp and -ΔH are shown in table 1.

EXAMPLE 16

TEGDVE was used as monomer. 2-Methyl-1,3-dihydroisothianaphtheniumhexafluoroantimonate according to structure B1 (below) was used asinitiator. Tp and -ΔH are shown in table 1.

EXAMPLE 17

TEGDVE was used as monomer. 2-Ethyl-1,3-dihydroisothianaphtheniumtetrafluoroborate according to structure B2 (below) was used asinitiator. Tp and -ΔH are shown in table 1.

EXAMPLE 18

TEGDVE was used as monomer.S-Methyl-2-(E-2-phenylethenyl)-[3,4]-benzo-2,5-dihydrothiopheniumhexafluorophosphate according to structure B3 (below) was used asinitiator. After dissolving the initiator B3 into the monomer, thepolymerization started within 10 minutes.

EXAMPLE 19

TEGDVE was used as monomer.S-Methyl-[3,4]-benzo-5-phenyl-2,7-dihydrothiepinium hexafluorophosphateaccording to structure C1 (below) was used as initiator. Tp and -ΔH areshown in table 1.

EXAMPLE 20

TEGDVE was used as monomer. 2-Ethyl-4-oxoisothiochromaniumtetrafluoroborate according to structure D1 (below) was used asinitiator. Tp and -ΔH are shown in table 1.

    ______________________________________                                        Structure A1-A10:                                                              ##STR12##                                                                    Structure   R.sup.1     R.sup.4   X.sup.-                                     ______________________________________                                        A1          CH.sub.3    H         SbF.sub.6.sup.-                             A2          CH.sub.3    H         PF.sub.6.sup.-                              A3          CH.sub.3    CH.sub.3  SbF.sub.6.sup.-                             A4          CH.sub.3    CH.sub.3  PF.sub.6.sup.-                              A5          CH.sub.3    OCH.sub.3 SbF.sub.6.sup.-                             A6          CH.sub.3    OCH.sub.3 PF.sub.6.sup.-                              A7          CH.sub.2 CH.sub.3                                                                         H         BF.sub.4.sup.-                              A8          CH.sub.2 CH.sub.3                                                                         CH.sub.3  BF.sub.4.sup.-                              A9          n-C.sub.4 H.sub.9                                                                         H         PF.sub.6.sup.-                               A10        n-C.sub.4 H.sub.9                                                                         OCH.sub.3 PF.sub.6.sup.-                              ______________________________________                                        Structure B1-B3:                                                               ##STR13##                                                                    Structure R.sup.1   R.sup.6     R.sup.7                                                                            X.sup.-                                  ______________________________________                                        B1        CH.sub.3  H           H    SbF.sub.6.sup.-                          B2        CH.sub.2 CH.sub.3                                                                       H           H    BF.sub.4.sup.-                           B3        CH.sub.3  CHCHC.sub.6 H.sub.5                                                                       H    PF.sub.6.sup.-                           ______________________________________                                        Structure C1:                                                                  ##STR14##                                                                    Structure   R.sup.1                                                                              R.sup.8    R.sup.9                                                                           X.sup.-                                     ______________________________________                                        C1          CH.sub.3                                                                             Ph         H   PF.sub.6.sup.-                              ______________________________________                                        Structure D1:                                                                  ##STR15##                                                                    Structure                                                                              R.sup.1       A       X.sup.-                                        ______________________________________                                        D1       CH.sub.2 CH.sub.3                                                                            ##STR16##                                                                            BF.sub.4.sup.-                                 ______________________________________                                    

                  TABLE 1                                                         ______________________________________                                        DSC-results from thermally induced cationic polymerizations                                                         -ΔH                               Example Initiator   Monomer   Tp (°C.)                                                                       (kJ/mol)                                ______________________________________                                        Compar. BTMS.sup.+ SbF.sub.6.sup.-                                                                TEGDVE    121.9   152.0                                   ex. 1                                                                         Compar. BTMS.sup.+ SbF.sub.6.sup.-                                                                EEC       147.8   142.4                                   ex. 2                                                                          1      A1          TEGDVE    124.9   159.7                                    2      A1          EEC       135.6   107.5                                    3      A2          TEGDVE    128.1   142.9                                    4      A2          EEC       157.3    57.6                                    5      A3          TEGDVE    103.2   155.1                                    6      A3          EEC       123.2   134.3                                    7      A4          TEGDVE    122.5   137.4                                    8      A5          TEGDVE     69.0   125.4                                    9      A5          EEC        91.8   127.1                                   10      A6          TEGDVE     65.5   127.0                                   11      A6          EEC        87.0    41.9                                   12      A7          TEGDVE    139.3   140.5                                   13      A8          TEGDVE    134.6   150.2                                   14      A9          TEGDVE    141.2   136.7                                   15      A10         TEGDVE     77.3   127.8                                   16      B1          TEGDVE    147.7   144.4                                   17      B2          TEGDVE    146.9   139.8                                   19      C1          TEGDVE    141.7   142.0                                   20      D1          TEGDVE    121.1   136.1                                   ______________________________________                                    

The peak temperature (Tp) is defined as the temperature at maximum heatflow and -ΔH is the heat of reaction per mole of monomer.

UV-initiated cationic polymerization

EXAMPLE 21

The polymerization was studied by the use of a Perkin-Elmer DSC-7differential scanning calorimeter, equipped with a DPA-7 double beamphotocalorimetric accessory including a 200 W high-pressureMercury-Xenon lamp (Hanovia 901-B0011). 1,0% by weight of the initiator2-ethyl-4-oxoisothiochromanium tetrafluoroborate, according to structureD1, was dissolved in TEGDVE. 2-3 mg of the solution was placed in analuminium pan, which was then mounted into the DSC. The sample wasirradiated isothermally at 20° C. for 4 minutes by the use of the lampdescribed above. The results from the exothermal cationic polymerizationwere: irradiation time to maximum heat flow (t_(p)) was 0.86 min andheat of polymerization (-ΔH) was 106.4 kJ/mol. A hard crosslinkedpolymer was found. No detectable odour from any organic sulfide orsulfur containing compound was noticed during or after thepolymerization.

Electron beam (EB) initiated cationic polymerization

Solutions were made by dissolving 0,75% (w/w) initiator in mixtures 90%(w/w) TEGDVE and 10% (w/w) CAB (cellulose acetate butyrate; thickener).Samples were coated on polyethylene sheets and irradiated under anitrogen atmosphere, using a Energy Sciences Electrocurtain. Applieddose was 1 Mrad.

Comparative example 3

BTMS⁺ SbF₆ ⁻, the same sulfonium salt initiator as in comparativeexamples 1 and 2 was used. A hard crosslinked polymer was found, but astrong odour of tetrahydrothiophene was noticable

EXAMPLE 22

2-Methyl-1,3-dihydroisothianaphthenium hexafluoroantimonate according tostructure B1 was used as initiator. A hard crosslinked polymer wasfound, and no detectable odour from organic sulfides or sulfurcontaining compounds was observed

Solubility test

In order to demonstrate the enhanced solubility of the initiators usedaccording to the present invention compared to previously developedinitiators, a less polar (more hydrophobic) monomer than TEGDVE waschosen, namely cyclohexyl vinyl ether (CHVE). In the two examples below,the sulfonium salts have the same anion (PF₆ ⁻).

Comparative example 4

BTMS⁺ PF₆ ⁻ (J. Polym. Sci., Polym. Lett. Ed., 1985, 23, 359) was verypoorly soluble in CHVE (80% w/w in acetone).

EXAMPLE 23

An 1% (w/w) homogeneous solution of initiator A9 was easily obtained inCHVE (80% w/w in acetone).

EXPERIMENTAL

Many different sulfonium salts of the general structures I and IIaccording to present invention, were synthesized and characterized.

Nuclear Magnetic Resonans (NMR) spectra were recorded on a 200 MHzBruker AC200 spectrometer. The chemical shifts are given in ppm (δ)relative to tetramethylsilane (internal standard). Melting points wererecorded on a Perkin-Elmer DSC-7 differential scanning calorimeter andUV-absorption spectra were recorded with a Perkin-Elmer Lambda 17 UV/VISspectrometer. All chemicals were purchased from Aldrich Chemical Co.

S-Methyl-2-phenyltetramethylenesulfonium hexafluoroantimonate (A1)

To a solution of 2-phenyltetrahydrothiophene (1,632 g, 10 mmol) (ageneral procedure for synthesis of 2-aryltetrahydrothiophenes wasapplied: D. L. Tuleen and R. H. Bennett, J. Heterocyclic Chem., 1969, 6,115) in 4 ml acetonitrile was methyl iodide (2.129 g, 15 mmol) added atambient temperature. After 24 the solvent was evaporated and 20 ml ofwater was added. The water phase was washed with diethyl ether severaltimes to remove unreacted starting material. NaSbF₆ (2.587 g, 10 mmol)was added. A yellow oil separated, which was extracted to a CH₂ Cl₂phase. The CH₂ Cl₂ phase was washed with an aqueous solution of Na₂ SO₃and water respectively and then dried with MgSO₄. Evaporation yielded63% of the desired product A1 as a mixture of two diastereomers. ¹ H-NMR(acetone-d₆) δ 7.4-7.7 (10 H, m, Ph-H), 5.63 (1 H, dd, J=5.7 and 12.0Hz, >S⁺ --CH--), 5.32 (1 H, dd, J=6.4 and 9.7 Hz, >S⁺ --CH--), 4.0-4.3(2 H, m, >S⁺ --CH₂ --), 3.6-3.9 (2 H, m, >S⁺ --CH₂ --), 3.32 (3 H, s,>S⁺ --CH₃), 2.56 (3 H, s, >S⁺ --CH₃), 2.4-3.2 (8 H, m, >S⁺ --CH₂--CH.sub. 2 --CH₂ --); Anal. Calcd for C₁₁ H₁₅ F₆ SSb: C, 31.8%; H,3.6%; S, 7.7%. Found: C, 32.7%; H, 3.8%; S, 8.7%.

S-Methyl-2-phenyltetramethylenesulfonium hexafluorophosphate (A2)

This compound was synthesized according to the procedure described forA1, but NaSbF₆ was replaced by KPF₆ (1.841 g, 10 mmol). A slowlycrystallizing oil of the diastereomeric mixture of A2 was obtained in67% yield. ¹ H-NMR (acetone-d₆) δ 7.4-7.7 (10 H, m, Ph-H), 5.61 (1 H,dd, J=5.7 and 11.9 Hz, >S⁺ --CH--), 5.31 (1 H, dd, J=6.4 and 9.7 Hz, >S⁺--CH--), 4.0-4.3 (2 H, m, >S⁺ --CH₂ --), 3.6-3.9 (2 H, m, >S⁺ --CH₂ --),3.29 (3 H, s, >S⁺ --CH₃), 2.54 (3 H, s, >S⁺ --CH₃), 2.4-3.0 (8 H, m, >S⁺--CH.sub. 2 --CH₂ --CH₂ --).

S-Methyl-2-(p-tolyl)tetramethylenesulfonium hexafluoroantimonate (A3)

This compound was synthesized according to the procedure described forA1 starting from 1.773 g (10 mmol) of 2-p-tolyltetrahydrothiophene. Aslowly crystallizing oil of the diastereomeric mixture of A3 wasobtained in 77% yield. ¹ H-NMR (acetone-d₆) δ 7.46-7.53 (4 H, m, Ar--H),7.27-7.37 (4 H, m, Ar--H), 5.57 (1 H, dd, J=5.8 and 11.9 Hz, >S⁺--CH--), 5.27 (1 H, dd, J=6.3 and 9.6 Hz, >S⁺ --CH--), 4.0-4.2 (2 H, m,>S⁺ --CH₂ --), 3.6-3.9 (2 H, m, >S⁺ --CH₂ --), 3.28 (3 H, s, >S⁺ --CH₃),2.53 (3 H, s, >S⁺ --CH₃), 2.38 (3 H, s, Ar--CH₃), 2.35 (3H, s, Ar--CH₃),2.3-3.0 (8 H, m, >S⁺ --CH₂ --CH₂ --CH₂ --); Anal. Calcd for C₁₂ H₁₇ F₆SSb: C, 33.6%; H, 4.0%; S, 7.5%. Found: C, 34.6%; H, 3.9%; S, 7.9%.

S-Methyl-2-(p-tolyl)tetramethylenesulfonium hexafluorophosphate (A4)

This compound was synthesized according to the procedure described forA1. The starting material was 1.773 g (10 mmol) of2-(p-tolyl)tetrahydrothiophene but NaSbF₆ was replaced by KPF₆ (1.841 g,10 mmol). A lightly yellow oil of a diastereomeric mixture of A4 wasobtained in 65% yield. ¹ H-NMR (acetone-d₆) 7.43-7.56 (4 H, m, Ar--H),7.23-7.43 (4 H, m, Ar--H), 5.60 (1 H, dd, J=5.8 and 11.9 Hz, >S⁺--CH--), 5.48 (1 H, dd, J=6.3 and 9.6 Hz, >S⁺ --CH--), 3.96-4.21 (2 H,m, >S⁺ --CH₂ --), 3.56-3.90 (2 H, m, >S⁺ --CH₂ --), 3.24 (3 H, s, >S⁺--CH₃), 2.53 (3 H, s, >S⁺ --CH₃), 2.39 (3 H, s, Ar--CH₃), 2.39 (3 H, s,Ar--Ch₃), 2.2-3.0 (8H, m, >S⁺ --CH₂ --CH₂ --CH₂ --)

S-Methyl-2-(p-methoxyphenyl)tetramethylenesulfonium hexafluoroantimonate(A5)

This compound was synthesized according to the procedure described forA1 starting from 1.933 g (10 mmol) of2-(p-methoxyphenyl)tetrahydrothiophene. A yellow oil of thediastereomeric mixture of A5 was obtained in 47% yield. ¹ H-NMR(acetone-d₆) δ 7.5-7.6 (4 H, m, Ar--H), 6.9-7.1 (4 H, m, Ar--H), 5.63 (1H, dd, J=5.6 and 12.1 Hz, >S⁺ --CH--), 5.32 (1 H, dd, J=6.4 and 9.5 Hz,>S⁺ --CH--), 4.0-4.3 (2 H, m, >S⁺ --CH₂ --), 3.85 (3 H, s, --O--CH₃),3.83 (3 H, s, --O--CH₃), 3.6-3.9 (2 H, m, >S⁺ --CH₂ --), 3.28 (3 H, s,>S⁺ --CH.sub. 3), 2.55 (3 H, s, >S⁺ --CH₃), 2.3-3.1 (8 H, m, >S⁺ --CH₂--CH₂ --CH₂ --); Anal. Calcd for C₁₂ H₁₇ F₆ SSb: C, 32.4%; H, 3.9%; S,7.2%. Found: C, 33.8%; H, 3.9%; S, 7.4%.

S-Methyl-2-(p-methoxyphenyl)tetramethylenesulfonium hexafluorophosphate(A6)

This compound was synthesized according to the procedure described forA1. The starting material was 1.933 g (10 mmol) of2-(p-methoxyphenyl)tetrahydrothiophene, but NaSbF₆ was replaced by KPF₆(1.841 g, 10 mmol). A yellow oil of a diastereomeric mixture of A6 wasobtained in 71% yield. ¹ H-NMR (acetone-d₆) δ 7.5-7.6 (4 H, m, Ar--H),6.9-7.1 (4 H, m, Ar--H), 5.63 (1 H, dd, J=5.6 and 12.1 Hz, >S⁺ --CH--),5.32 (1 H, dd, J=6.4 and 9.5 Hz, >S⁺ --CH--), 4.0-4.3 (2 H, m, >S⁺ --CH₂--), 3.85 (3 H, s, --O--CH₃), 3.83 (3 H, s, --O--CH₃), 3.6-3.9 (2 H,m, >S.sup. + --CH₂ --), 3.28 (3 H, s, >S⁺ --CH₃), 2.55 (3 H, s, >S⁺--CH₃), 2.3-3.1 (8 H, m, >S⁺ --CH₂ --CH₂ --CH₂ --).

S-Ethyl-2-phenyltetramethylenesulfonium tetrafluoroborate (A7)

2-Phenyltetrahydrothiophene (1.632 g, 10 mmol) (J. Heterocyclic Chem.,1969, 6, 115) was dissolved in 10 ml of dry CH₂ Cl₂ at 0° C. To thissolution, which was kept under N₂, 10 ml of triethyloxoniumtetrafluoroborate (10 mmol; 1M solution in CH₂ Cl₂) was added. Then thereaction mixture was stirred for 5 h at ambient temperature. Evaporationof solvent gave an oil that was washed with diethyl ether several times.After dissolving the oil in CH₂ Cl₂ the organic phase was washed withwater, dried with MgSO₄ and evaporated. A yellow oil was obtained in 76%yield as a 2.4/1 mixture of two diastereomers of A7. ¹ H-NMR(acetone-d₆) δ 7.8-7.4 (5 H, m, Ph-H), 5.7-5.3 (1 H, >S⁺ --CH--),including 5.64 (dd, J=5.4 and 12.4 Hz, minor isomer) and 5.38 (dd, J=6.4and 10.1 Hz, major isomer)), 4.2-3.0 (4 H, m, >S⁺ --CH₂ --), 3.0-2.4 (4H, m, >S⁺ --CH₂ --CH₂ --CH₂ --), 1.55 (t, J=7.4 Hz, CH₃ is majorisomer), 1.01 (t, J=7.4 Hz, CH₃ in minor isomer).

S-Ethyl-2-(p-tolyl)tetramethylenesulfonium tetrafluoroborate (A8)

Triethyloxonium tetrafluoroborate 10 ml (10 mmol; 1M solution in CH₂Cl₂) was added to a 10 ml dry solution of 1.773 g (10 mmol) of2-(p-tolyl)tetrahydrothiophene in CH₂ Cl₂ according to the proceduredescribed for A7. A yellow oil of a diastereomeric mixture of A8 wasobtained in 76% yield. ¹ H-NMR (acetone-d₆) δ 7.52-7.56 (4 H, m, Ar--H),7.28-7.37 (4 H, m, Ar--H), 5.64 (1 H, dd, J=5.8 and 11.8 Hz, >S⁺--CH--), 5.37 (1 H, dd, J=6.3 and 9.9 Hz, >S⁺ --CH--), 4.0-4.2 (2 H, m,>S⁺ --CH₂ --CH₂ --), 3.6-3.9 (2 H, m, >S⁺ --CH₂ --CH₂ --), 3.65 (2 H, q,>S⁺ --CH₂ --CH₃), 2.35 -3.25 (10 H, m, >S⁺ --CH₂ --CH₂ --CH₂ --, >S⁺--CH₂ --CH₃), 2.37 (3H, s, Ar--CH₃), 2.34 (3H, s, Ar--CH₃), 1.51 (3 H,t, J=7.4 Hz, >S⁺ --CH₂ --CH₃, 1.00 (3H, t, J=7.4 Hz, >S⁺ --CH₂ --CH₃).

S-(n-Butyl)-2-phenyltetramethylenesulfonium hexafluorophosphate (A9)

2-(p-tolyl)tetrahydrothiophene (1.773 g, 10 mmol) was alkylated with1-butyl iodide (2.76 g, 15 mmol) according to the procedure describedfor compound A1 but NaSbF₆ was replaced by KPF₆ (1.841 g, 10 mmol). Alightly yellow oil of a diastereomeric mixture of A9 was obtained in 25%yield. ¹ H-NMR (acetone-d₆) 7.4-7.8 (10 H, m, Ph-H), 5.69 (1 H, dd, >S⁺--CH--), 5.43 (1 H, dd, >S⁺ --CH--), 3.5-4.2 (8 H, m, >S⁺ --CH₂ --),2.40-3.25 (8 H, m, >S⁺ --CH₂ --CH₂ --CH₂ --CH--), 1.15-2.0 (8 H, m, CH₃--CH₂ --CH₂ --), 0.91 (3 H, t, CH₃ --), 0.73 (3 H, t, CH₃ --).

S-(n-Butyl)-2-(p-methoxyphenyl)tetramethylenesulfoniumhexafluorophosphate (A10)

This compound was synthesized according to the procedure described forA1. The starting material was 1.933 g (10 mmol) of2-(p-methoxyphenyl)tetrahydrothiophene and 2.76 g (15 mmol) of 1-butyliodide. Instead of NaSbF₆ 1.841 g (10 mmol) of KPF₆ was used. A lightlyyellow oil of a diastereomeric mixture of A10 was obtained in 21% yield.¹ H-NMR (acetone-d₆) δ 7.55-7.67 (4 H, m, Ar--H), 6.98-7.13 (4 H, m,Ar--H), 5.65 (1 H, dd, J=5.5 and 12.2 Hz, >S⁺ --CH--), 5.38 (1 H, dd,J=6.5 and 10.7 Hz, >S⁺ --CH--), 3.5-4.2 (8 H, m, >S⁺ --CH₂ --), 3.86 (3H, s, Ar--CH₃), 3.84 (3 H, s, Ar--CH₃ ), 2.40-3.25 (8 H, m, >S⁺ --CH₂--CH₂ --CH₂ --CH--), 1.15-2.0 (8 H, m, CH₃ --CH₂ --CH₂ --), 0.93 (3 H,t, CH₃ --), 0.76 (3 H, t, CH₃ --).

2-Methyl-1,3-dihydroisothianaphthenium hexafluoroantimonate (B1)

To 1,3-dihydroisothianaphthene (1.326 g, 10 mmol) (J. A. Oliver and P.A. Ongley, Chem. Ind. (London), 1965, 1024) dissolved in 3 ml of acetonewas added 2.129 g (15 mmol) methyl iodide under N₂ at ambienttemperature. After 24 h of stirring the solvent was evaporated. Theresidue was washed with diethyl ether to remove unreacted startingmaterial, giving white crystals of2-methyl-1,3-dihydroisothianaphthenium iodide 2.251 g (81%).

To a well stirred solution of 20 ml of ethanol kept at ambienttemperature 0.319 g (1.86 mmol) of AgSbF₆ and 0.259 g (1.86 mmol) of2-methyl-1,3-dihydroisothianaphthenium iodide was added. After 2 h 0.214g of AgI (s) could be filtered off. Evaporation of the remaining ethanolsolution gave 0.344 g (95.5%) of 2-methyl-1,3-dihydroisothianaphtheniumhexafluoroantimonate as white crystals. mp=126.2° C.; ¹ H-NMR(acetone-d₆) δ 7.39-7.55 (4 H, m, Ar--H), 4.90 (2 H, d, J=16.0 Hz, >S⁺--CH--), 4.59 (2 H, d, J=16.0 Hz, >S⁺ --CH--), 2.71 (3 H, s, >S⁺ --CH₃--); ¹³ C-NMR (acetone-d₆) δ 133.8, 128.3, 125.9, 48.1, 23.9.

2-Ethyl-1,3-dihydroisothianaphthenium tetrafluoroborate (B2)

Triethyloxonium tetrafluoroborate 10 ml (10 mmol; 1M solution in CH₂Cl₂) was added to a 10 ml dry solution of 1.326 g (10 mmol) of1,3-dihydroisothianaphthene (Chem. Ind. (London), 1965, 1024) at 0° C.The reaction mixture was kept under N₂ and was stirred for 5 h.Evaporation of the solvent resulted in a black oil that crystallizedupon treatment with diethyl ether. Recrystallization from ethanol gavewhite crystals in 53% yield. mp=75.3° C.; ¹ H-NMR (acetone-d₆) δ 7.4-7.6(4 H, m, Ar--H), 5.17 (2 H, d, J=17.1 Hz, >S⁺ --CH--Ar), 4.97 (2 H, d,J=17.1 Hz, >S⁺ --CH--Ar), 3.45 (2 H, q, >S⁺ --CH₂ --CH₃), 1.50 (3 H, t,>S⁺ --CH₂ --CH₃); ¹³ C-NMR (acetone-d₆) δ 135.05, 129.79, 126.75, 46.97,36.76, 9.35; Anal. Calcd for C₁₀ H₁₃ BF₄ S: C, 47.7%; H, 5.2%; S, 12.7%.Found: C, 47.9%; H, 5.2%; S, 12.5%.

S-methyl-2-(E-2-phenylethenyl)-[3,4]-benzo-2,5-dihydrohydrothiopheniumhexafluorophosphate (B3)

To a stirred solution of lithium thiomethoxide (82.19 mmol, generatedfrom n-BuLi and methylmercaptan) in 130 ml of ethanol/THF (2:3)2-bromobenzylbromide (12.54 g, 50.17 mmol) was added. After 1 h ofreflux 30 ml of a saturated aqueous NH₄ Cl solution was added. Themixture was concentrated and extracted with ether The organic phase waswashed with water and dried with MgSO₄. After evaporation the crudeproduct was distilled to give a clear liquid of o-bromobenzyl methylsulfide 9.88 g (89%).

Butyl lithium (2.96 ml, 4.61 mmol, 1.58M in hexane) was added to a 2 mlTHF solution of o-bromobenzyl methyl sulfide (1.0 g, 4.61 mmol) kept at-70° C. and under N₂. After 10 minutes the temperature was raised to-30° C. and kept there for 35 minutes before cinnamic aldehyde (0.61 g,4.61 mmol) dissolved in 2 ml of THF was added. The reaction was quenched1 h later by addition of 250 μl of water. The organic part of thereaction mixture was concentrated and CH₂ Cl₂ was added. After washingwith water the CH₂ Cl₂ solution was dried with MgSO₄, filtered and thenevaporated. Flash chromatography, using CH₂ Cl₂ /petroleum ether (85:15)as eluent, yielded 0.68 g (55%) of(o-thiomethoxymethylphenyl)-E-(2-phenylethenyl)carbinol as an oil.

Hexafluorophosphoric acid (60% in water, 452 mg, 1.857 mmol) was addedto a solution of (o-thiomethoxymethylphenyl)-E-(2-phenylethenyl)carbinol(251 mg, 0.928 mmol) in 4 ml of acetic acid anhydride kept at 0° C. Thereaction mixture was stirred for 5 h and then the solvent wasevaporated. The crude material was dissolved in CH₂ Cl₂. This solutionwas washed with water, dried (MgSO₄), filtered and then the solvent wasevaporated to give 199 mg (54%) of brownish grey crystals of B2 as a1.3/1 mixture of two diastereomers ¹ H-NMR (acetone-d₆) δ majordiastereomer: 7.2-7.7 (9 H, m, Ar--H), 6.74 (1H, d, J=15.8 Hz, ═CH--Ph),6.58 (1 H, dd, J=8.1 and 15.8 Hz, --CH═CH--Ph), 5.99 (1 H, d, J=8.1 Hz,--CH--CH═CH--Ph), 5.23 (1 H, d, J=16.6 Hz, >S⁺ --CHH--), 4.70 (1 H, d,J=16.6 Hz, >S⁺ --CHH--), 2.89 (3 H, s, CH₃), minor diastereomer: 7.2-7.7(9 H, m, Ar--H), 7.15 (1 H, d, J=15.4 Hz, ═CH--Ph), 6.50 (1 H, dd, J=9.2and 15.4 Hz, --CH═CH--Ph), 6.34 (1 H, d, J=9.2 Hz, --CH--CH═CH--Ph),5.05 (1 H, d, J=16.1 Hz, >S⁺ --CHH--), 4.73 (1 H, d, J=16.1 Hz, >S⁺--CHH--), 2.73 (3 H, s, CH₃).

S-Methyl-5-phenyl-[3,4]-benzo-2,7-dihydrothiepinium hexafluorophosphate(C1)

2-(Bromomethyl)benzonitrile (20.4 g, 103 mmol) was added to suspensionof lithium thiometoxide (12.62 g, 181 mmol) in ethanol (35 mL). Afterthe reaction mixture was refluxed for 2 h, aqueous NH₄ Cl (50 mL) wasadded. The resulting mixture was concentrated ad extracted with ether.The combined ether phase was washed with H₂ O and brine, dried, andconcentrated to give 16.0 g (95%) of 2-(thiomethoxymethyl)-benzonitrileas a light yellow liquid.

A THF-solution of phenyl magnesium bromide (30.6 mL, 45.6 mmol) wasadded to 2-(thiomethoxymethyl)-benzonitrile (5.0 g, 30.6 mmol) in THF (6mL) at ambient temperature under a N₂ -atmosphere. The reaction mixturewas refluxed for 4 h, allowed to cool, quenched with 6M HCl (40 mL).After reflux for additional 16 h the reaction mixture was neutralizedwith Na₂ CO₃ (aq. saturated) and extracted with methylene chloride. Theorganic phase was washed with H₂ O, dried, and concentrated to give acrude product which was purified by chromatography (SiO₂) yielding 5.17g (70%) of 2-(thiomethoxymethyl)-benzophenone as a light yellow liquid.

To a solution of 2-(thiomethoxymethyl)-benzophenone (2.0 g, 8.37 mmol)in THF (5 mL) was added a THF-solution of vinyl magnesium bromide (16.7mL, 16.7 mmol) at RT under a N₂ -atmosphere. After reflux for 2 h, satNH₄ Cl (aq) was added. Concentration followed by ether extractionyielded an organic phase which was washed with H₂ O, dried (MgSO₄), andconcentrated to give 1.79 g (77%) ofphenyl(2-thiomethoxymethyl)phenyl-vinylcarbinol.

To a mixture of phenyl-(2-thiomethoxymethyl)phenyl-vinylcarbinol (1.63g, 6 mmol) and acetic anhydride (12 mL) was added hexafluoro phosphoricacid (60% in water, 1.94 g) and the mixture was stirred for 5 h at 0° C.The mixture was concentrated and dissolved in methylene chloride. Theorganic phase was washed with water and NaHCO₃ (aq, satur). Drying(MgSO₄) and concentrated gave 1.67 g (70%) of C1 as light browncrystals. ¹ H-NMR (acetone-d₆) δ 7.0-7.7 (9 H, m, Ar--H), 6.6 (1 H, t,J=7 Hz, ═CH--), 4.63 (1 H, d, J=13 Hz, Ar--CH--), 4.26 (1 H, d, J=13 Hz,Ar--CH--), 3.82-4.05 (1 H, m, >S⁺ --CHH--CH═), 3.3-3.5 (1 H, m, >S⁺--CHH--CH═), 2.85 (3 H, s, >S⁺ --CH₃ --); UV-absorption max. (ethanol):203, 239 nm.

2-Ethyl-4-oxoisothiochromanium tetrafluoroborate (D1)

1.642 g (10 mmol) isothiochroman-4-one (J. Am. Chem. Soc. 1973, 95,2923) was alkylated with triethyloxonium tetrafluoroborate (10 mmol, 1Min methylene chloride) according to the method described for compoundB2. Recrystallization in ethanol gave 1.26 g (50%) of D1 as whitecrystals; mp=89.6° C. ¹ H-NMR (acetone-d₆) δ 7.65-8.14 (4 H, m, Ar--H),5.23 (1 H, d, J=16.1 Hz, --CHH--C(O)--), 5.03 (1 H, d, J=16.1 Hz,--CHH--C(O)--), 4.80 (1 H, d, J=17.2 Hz, --CHH--Ar), 4.55 (1 H, dd,J=2.0 and 17.2 Hz, --CHH--Ar), 3.45-3.85 (2 H, m, >S⁺ --CH₂ --CH₃), 1.55(3 H, t, J=7.5 Hz, >S⁺ --CH₂ -- CH₃); ¹³ C-NMR (acetone-d₆) δ 183.64,136.04, 131.78, 130.97, 130.75, 130.51, 128.93, 40.06, 34.45, 34.40,8.85; UV-absorption max. (ethanol): 254, 293 nm; Anal. Calcd for C₁₁ H₁₃BF₄ OS: C, 47.2%; H, 4.7%; S, 11.5%. Found: C, 47.3%; H, 4.6%; S, 11.5%.

We claim:
 1. In a method of cationic polymerization of at least onecationically polymerizable monomer in the presence of a polymerizationinitiator, the improvement wherein said polymerization initiator is aheterocyclic, aryl substituted or with an aryl ring fused sulfonium saltwith a non-nucleophilic anion, wherein the sulfonium group is positionedso that the sulfonium salt is ring-opened by activation whereby astabilized carbocation capable of initiating cationic polymerization isformed together with a sulfide, which is covalently bonded to thecationic fragment, and which sulfonium salt has one of the followingstructural formulae ##STR17## wherein m=an integer between 3 and 5n=aninteger between 1 and 3 z=an integer between 0 and 3 y=an integerbetween 0 and 4 X=represents a group of the formula MY_(r) (1) or theformula Q(2),wherein in MY_(r) (1): M=Sb, As, P, B or Cl; Y represents ahalogen or O and where r is an integer between 4 and 6, the formula Q(2)represents a sulfonic acid R-SO₃ wherein R is an alkyl, aryl group, ahalogen-substituted alkyl or a halogen-substituted aryl group, R¹represents an alkyl, cycloalkyl group, or an aryl group, R² representshydrogen, an alkyl, alkenyl, cycloalkenyl, cycloalkyl group, or arylgroup, all R² being independent of each other, R³ represents hydrogen,an alkyl, alkenyl, cycloalkenyl, cycloalkyl group, or aryl group, all R³being independent of each other, R⁴ represents hydrogen, halogen, analkenyl a cycloalkenyl, an alkyl cycloalkyl group, an alkoxy, thioalkoxygroup, a hydroxyl- or alkyl (C₁ -C₁₂) terminated poly(alkyleneoxide)group with up to 10 alkyleneoxide units, an aryl group, an aryloxy orthioaryloxy group, R⁵ represents halogen, an alkyl, cycloalkyl group, analkoxy, thioalkoxy group, a hydroxyl- or alkyl (C₁ -C₁₂) terminatedpoly(alkyleneoxide) group with up to 10 alkyleneoxide units, an arylgroup, an aryloxy or thioaryloxy group,wherein in structure I R⁴ or R⁵(y=1-2) also can be the group ##STR18## R⁶ represents hydrogen, analkyl, alkenyl, cycloalkenyl, cycloalkyl group, an aryl group, R⁷represents hydrogen, an alkyl, alkenyl, cycloalkenyl, cycloalkyl group,or an aryl group, A represents ##STR19## or a single bond, R⁸ representshydrogen, an alkyl, cycloalkyl group, a hydroxyl- or alkyl(C₁-C₁₂)terminated poly(alkyleneoxide) group with up to 10 alkyleneoxideunits, an aryl group, an aryloxy or thioaryloxy group, R⁹ representshydrogen, an alkyl, cycloalkyl group, hydroxyl- or alkyl(C₁-C₁₂)terminated poly(alkyleneoxide) group with up to 10 alkyleneoxideunits an aryl group, an aryloxy or thioaryloxy group, or R⁸ and R⁹together form an aryl ring fused with the heterocyclic sulfonium ring,said aryl ring optionally being substituted with a group R¹⁰ which canbe a halogen atom, a nitro group, an alkyl, cycloalkyl group, alkoxy,tihoalkoxy group, a hydroxyl- or alkyl(C₁ -C₁₂)terminatedpoly(alkyleneoxide) group with up to 10 alkyleneoxide units, an arylgroup, an aryloxy or thioaryloxy group, said polymerization beingcarried out by means of thermal activation, photochemical activation (UV-irradiation) or activation by electron bombardment (EB).
 2. The methodaccording to claim 1, wherein the sulfonium salt has the structuralformula I wherein m=3, X=MY_(r), R² =H, R³ =H and R⁶ =H och y, R¹, R⁴,R⁵, M, Y and r are as defined in claim
 1. 3. The method according toclaim 2, wherein R⁴ is ##STR20## and y, R¹ and R⁵ are as defined inclaim
 1. 4. The method according to claim 1, wherein the sulfonium salthas the structural formula ##STR21## wherein R¹ is methyl, ethyl orn-butyl, R⁴ is hydrogen, methyl eller methoxy and X⁻ is SbF₆ ⁻, PF₆ ⁻ orBF₄ ⁻.
 5. The method according to claim 4, wherein the sulfonium salt isselected fromS-methyl-2-phenyltetramethylenesulfoniumhexafluoroaantimonate, S-methyl-2-phenyltetramethylenesulfoniumhexafluorophosphate, S-methyl-2-(p-tolyl)tetramethylenesulfoniumhexafluoroantimonate, S-methyl-2-(p-tolyl)tetramethylenesulfoniumhexafluorophosphate, S-methyl-2-(p-methoxyphenyl)tetramethylenesulfoniumhexafluoroantimonate,S-methyl-2-(p-methoxyphenyl)tetramethylenesulfonium hexafluorophosphate,S-ethyl-2-phenyltetramethylenesulfonium tetrafluoroborate,S-ethyl-2-(p-tolyl)tetramethylenesulfonium tetrafluoroborate,S-(n-butyl)-2-phenyltetramethylenesulfonium hexafluorophosphate orS-(n-butyl)-2-(p-methoxyphenyl)tetramethylenesulfoniumhexafluorophosphate.
 6. The method according to claim 1, wherein thesulfonium salt has the structural formula II wherein A is ##STR22## n=1,R² =H, R³ =H, R⁶ =H, R⁷ =H, X=MY_(r) and z, R¹, R⁴ and R⁵, M, Y and rare as defined in claim
 1. 7. The method according to claim 6, whereinthe sulfonium salt is 2-ethyl-4-oxoisothiochromanium tetrafluoroborateof the structural formula ##STR23##
 8. The method according to claim 1,wherein the sulfonium salt has the structural formula II wherein A is##STR24## n=1, X=MY_(r), and z, R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, R⁹, M, Yand r are as defined in claim
 1. 9. The method according to claim 1,wherein the sulfonium salt has the structural formula II wherein A is asingle bond, n=1-2, X=MY_(r), and z, R¹, R², R³, R⁴, R⁵, R⁶, R⁷, M, Yand r are as defined in claim
 1. 10. The method according to claim 1,wherein the sulfonium salt has the structural formula ##STR25## whereinR¹ is methyl or ethyl, R⁶ is hydrogen or phenylethenyl, R⁷ is hydrogenand X⁻ is SbF₆ ⁻, PF₆ ⁻ or BF₄ ⁻.
 11. The method according to claim 10,wherein the sulfonium salt is selected from2-methyl-1,3-dihydroisothianaphthenium hexafluoroantimonate,2-ethyl-1,3-dihydroisothianaphthenium tetrafluoroborate ellerS-methyl-2-(2-phenylethenyl)-[3,4]-benzotetrahydrothiopheniumhexafluorophosphate.
 12. An aryl substituted cyclic sulfonium salt ofthe structural formula ##STR26## which isS-methyl-2-phenyltetramethylenesulfoniumhexafluoroaantimonate,S-methyl-2-phenyltetramethylenesulfoniumhexafluorophosphate, S-methyl-2-(p-tolyl)tetramethylenesulfoniumhexafluoroantimonate, S-methyl-2-(p-tolyl)tetramethylenesulfoniumhexafluorophosphate, S-methyl-2-(p-methoxyphenyl)tetramethylenesulfoniumhexafluoroantimonate,S-methyl-2-(p-methoxyphenyl)tetramethylenesulfonium hexafluorophosphate,S-ethyl-2-phenyltetramethylenesulfonium tetrafluoroborate,S-ethyl-2-(p-tolyl)tetramethylenesulfonium tetrafluoroborate,S-(n-butyl)-2-phenyltetramethylenesulfonium hexafluorophosphate orS-(n-butyl)-2-(p-methoxyphenyl)tetramethylenesulfoniumhexafluorophosphate.
 13. The method according to claim 1 wherein,eachhalogen in Y is F or Cl, each halogen-substituted group in R issubstituted by F or Cl, each alkyl, cycloalkyl, cycloalkenyl, alkoxy orthioalkoxy group has 1-20 carbon atoms, and the alkenyl group in R⁴ is avinyl group.